T3_Homeostasis

Homeostasis Overview

• Definition: Homeostasis is the ability of the body to maintain relatively stable internal conditions despite continuous changes in the external environment (Walter Cannon).

• Characteristics:

  • Equilibrium: Involves dynamic equilibrium in various systems.

  • Vital Nutrients: Maintains adequate blood levels of essential nutrients.

  • Heart Activity: Monitors and adjusts heart activity and blood pressure.

  • Waste Management: Ensures that wastes do not accumulate.

  • Body Temperature: Regulates and maintains body temperature.

Survival Needs

• Nutrients: Essential chemicals for energy and cell building.

• Oxygen: Needed for energy release via ATP production.

• Water: Crucial for chemical reactions and bodily functions (secretions, excretions).

• Normal Body Temperature: Approximately 37°C, which affects the rate of chemical reactions.

• Atmospheric Pressure: Necessary for adequate breathing and gas exchange.

Homeostatic Control Mechanisms

1. Stimulus: Identifies an imbalance.

2. Receptors: Detect changes in the internal environment.

3. Control Center: Receives and processes information from receptors.

4. Efferent Pathway: Communicates responses to effectors.

5. Effectors: Carry out responses to restore balance.

6. Feed-back Mechanism: Responds to the change to bring about a final response, reducing further stimulus.

Feedback Mechanisms

• Negative Feedback:

  • Most common, reduces or shuts off the original stimulus.

  • Examples include regulation of body temperature and blood volume by ADH.

• Positive Feedback:

  • Enhances or exaggerates the original stimulus.

  • Examples include labor contractions and blood clotting.

Autonomic Nervous System (ANS)

• Division: Divided into the Sympathetic and Parasympathetic systems.

• Sympathetic Division: Mobilizes the body during activity (fight-or-flight response).

  • Increases heart rate and blood pressure, dilates airways, and releases glucose for energy.

• Parasympathetic Division: Active during non-stress situations (rest and digest).

  • Promotes digestion and conserves energy by reducing heart rate and blood pressure.

Cooperation of SNS and ANS

• Dynamic Interaction: Allows precise control of visceral activity, essential for maintaining homeostasis.

• Organ Regulation: Most visceral organs innervated by both divisions with opposing effects.

Endocrine System Overview

• Functions: Regulates growth, metabolism, body fluids, reproductive processes, and defense mechanisms.

• Communication: Relies on hormones, which are chemical messengers released into the bloodstream, affecting target organs and processes.

Hormones and Their Functions

• Types: Hormones can be classified as amino acid-based or steroid hormones.

• Receptors: Only target cells with specific receptors respond to a hormone's message.

• Mechanisms:

  • Water-Soluble Hormones: Interact with membrane receptors and use second-messenger systems.

  • Lipid-Soluble Hormones: Cross cell membranes and affect intracellular receptors, leading to direct gene activation.

Neuroendocrine System

• Integration: Combines the fast responses of the nervous system with the slower but longer-lasting effects of the endocrine system.

• Homeostasis Maintenance: Critical for maintaining homeostasis by regulating physiological responses through hormonal and neural signals.